A Dictionary of Music and Musicians/Point d'Orgue
POINT D'ORGUE, organ point, appears to have two different meanings in French, and to be used (1) for an organ point or pedal, that is, a succession of harmonies carried over a holding note [Pedal]; and (2), with what reason is not plain, for the cadenza in a concerto—the flourish interpolated between the chords of the 6-4 and 7-3 of the cadence—the place for which is indicated by a pause 
. Rousseau gives a clue to the origin of the term by explaining (under 'Couronne') that when the above sign, which he denominates 'Couronne,' was placed over the last note of a single part in the score it was then called Point d'orgue, and signified that the sound of the note was to be held on till the other parts had come to the end. Thus the note so held on became a pedal, and is so in theory.
. Rousseau gives a clue to the origin of the term by explaining (under 'Couronne') that when the above sign, which he denominates 'Couronne,' was placed over the last note of a single part in the score it was then called Point d'orgue, and signified that the sound of the note was to be held on till the other parts had come to the end. Thus the note so held on became a pedal, and is so in theory. [ G. ]